Telephone system



Feb. 20, 1945. R TAYLOR ET AL 2,369,868

' TELEPHONE SYSTEM Filed April 15, 1940 10 Sheets-Sheet 1 Illllll DTUPCRS 9 mlunu m mentors REGINALD TAYL 0P GEORGE THOMAS BAKER AttorneyFeb. 20, 1945.

R. TAYLOR ET AL TELEPHONE SYSTEM Filed April 15, 1940 l0 Sheets-Sheet 2Mme/Mars REG/WALD TAYLOR 5g gee/vetmoms BAKER Attorney Feb. 20, 1945. R.TAYLOR ET AL. 2,369,868

7 TELEPHONE SYSTEM Filed April 15, 1940 10 Sheets-Sheet 5' lllHlllll //7V6 174 ors REGINALD TAYLOR 5y GfORGE THOMAS BAKER Attomy Feb. 20, 1945.

R. TAYLOR ET AL TELEPHONE SYSTEM Filed April 15, 1940 PAS E I 10Sheets-Sheet 4 llllllllll g 3 l|lllll|l|U- l lnvehtors REG/NA LD 7A YLORGEORGE THOMS BAR Attorney -20, 1945 R. Wm ET AL 2,369,868

7 TELEPHONE SYSTEM Filed April 15, 1940 10 Sheets-Sheet 5 IZIS ICS

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v uunyjg l-IHHIIIIQ- a //7| en0rs REGINALD TAYLOR 6%565 THOMAS BAKEAha/nay 1945- R. TAYLOR ET AL TELEPHONE SYSTEM Filed April 15, 1940 10Sheets-Sheet 6 I/Zit D MRA IMP5 mus PS", J

/A 4/A -4.. a 551 I M as H" /n Mentors REGINALD TAYLOR 5 apes THOMAS BAKFeb. 20, 1945. R, TAYLOR ET AL 2,369,868

TELEFHONE SYSTEM Filed April 15, 1940 16 Sheets-Sheet v 5m? mvent'orsREG/NALD TAYLOR Z GEORGE THOMAS BAKER Feb. 20, 1945. 4 R TAYLOR ET AL2,369,868

TELEPHONE SYSTEM Filed April 1 5, 1940 10 Sheets-Sheet s' E/[vl /U WtIMPA Myento/s REG/MILD 7I4YLOR 5 GEORGE THOMAS BAKER Feb. '20, 1945. R.TAYLOR ET AL TELEPHONE SYSTEM Filed April 15, 1940 10 Sheets-Sheet 9 /nventors REGINALD TA YLOR GEORGE THOMAS BAKER Afton? e51 Feb. 20, 1945. TYL R ET AL 2,369,868

TELEPHONE SYSTEM Filed April 15} 1940 10 Sheets-Sheet 1Q f/E. /Z

Patented Feb. 20, 1945 TELEPHONE SYSTEM Reginald Taylor and GeorgeThomas Baker, piverpool, England, assignors, by mesne assignments, toAutomatic Electric Laboratories, Inc.,'

Chicago, Ill.,'a corporation of Delaware Applicants April 15, 1940,Serial No. 329,608.

. I In Great Britain May 5, 1939 27 Claims. (c1. 179-71) Thepresentinvention. concerns improvements in or relating to arrangementsfor setting ,up' connections in telephone systems and is moreparticularly concerned with improved arrangements for dealingwith;connections which re- ,quireto be recorded for charging purposes,that is to; say, connections which come outside the range in which thecharge maybe determined by operating a meter individual to a callingsubscriber one or more times and whereby such calls may be charged onthe basis of duration as well as distance. a Generally speaking it isusual for connections local to an exchange area having a linkednumbering scheme to be charged by operating the subscribers individualmeter and in addition, thereby exchanges are also charged in thismanner, although they are not in the area having the ,same linkednumbering scheme as the area in which the call originates.

The characteristic feature, of the present invention is that callrecording is adapted to, take place at the'sameexchange in an area asthat at which the route to the destination exchange is determined, sothat the number of the subscriber. wanted inthe linked numbering schemewith which the destination exchange is associated is transmitted iniullfrom the originating area direct to ,the' destination area aiter thecall has 'beenset up to an exchange in the destination area, while therecording takes place at the exchange in the originating area from whichsuch number is transmitted. 4

This invention may be applied in a variety of circumstances, forinstancaexchanges at present in existence may be broadly classified intotwo different types, in one of which the linked numbering scheme is upona decimal basis, and each subscribers number in the area covered by thelinked numbering scheme has a given number of digits, for instance, 4, 5or 6, each of which digits is represented by the setting of switches forestablishing a connection having a direct numerical relation thereto. Asecond type of area is one in whichthelinked numbering scheme is basedupon the initial digits representing an exchange name, and other digitsrepresenting the number of the subscriber. attached to that ex change;Frequently, sucfh exchange designating digits are represented byletters, and are caused by means of a register-translator to betranslated into routing digits 'for transferring the call from theoriginating to the destination exchange the setting of the switches forsuch routing having no numerical relation to the numerical values-whichmay be assigned to such exchange-designating digits. On the other handthe numerical digits correspond to the setting of the switches in thedestination exchange required to establish connection to a subscriber.

In this specification the first class of linked numbering scheme will bereferred to as a nonregister-translator network and the second form oflinked numbering schemewill be referred to 'as'a register-translatornetwork.

The invention has application to setting up calls between .onenon-register-translator network and ,another non-register-translatornetwork, between a register-translator network and anon-register-translator network, between a non-register-translatornetwork and a registertranslator network, between a register-translatornetwork and another register-translator network and between aregister-translator network and exchanges in the near vicinity of suchnetwork which may be of such a .distance as to necessitate thedesirability of call recording facilities but otherwise are such thatthey could be included in the register-translator network.

It will be appreciated that generally speaking the register translatornetworks are of'very much greater extent than thenon-register-translator networks.

At present in non-register-translator networks requ'ring say 5 or 6digit numbers, metering is usually performed on a unit'fee basis, thatis to say for local calls a single operation of a calling apparatusmeter is effected while long distance calls are routed via amanualoperator, for instance, by dialing 0.

In other cases a number of adjacent nonregister-translator networks arecombined into a composite network of reasonable size. Intercommunicationbetween various networks is made by dialling the required wanted numberon th called network together with one or more prefix digits indicatingsuch network. As each non-register-translator network will usually haveits own linked numbering scheme, and with a view to keeping the numberof digits down to a minimum, say nomore than 7 when calling from oneregister-translator network to another in the composite network, asimplified form of registertranslator or route-discriminator isassociated with the outgoing junctions of each network so as to routethe call to the desired network.

Such networks may be arranged to operate on a multi-fee basis.jThenumber of times a sub: scribers meter is operated in response to thesetting up or a callis determined by the routediscriminator inaccordance with the particular number dialled. For calls outside thecomposite areas access to a manual number will usually be obtained bydialling 0.

Thirdly, in the case Ofcongested multi-exchange networks,register-translators will be used on all calls Within the network,irrespective of Whether the calling party is on the originating exchangeor not, and in this case multi-fee metering facilities can readily beincorporated. The number of times a subscribers meter is operated for agiven cause may for instance be determined in accordance with theparticular level to. which the first or second code selector switch isset by the register-translator. For calls outside such areas the codeletters TOL or TRU may be dialled and the calling party will be routedto a manual board at a toll or trunk exchange respectively.Alternatively, access can be had to an operator by simply dia1ling"0.

One of the applications of the invention is to the extension. of suchnetworks, in view of the use of call recording or automatic ticketingapparatus, tov a size whereby subscriber dialling may become a feasibleproposition over distances hitherto. requiring the charging. of a fee byan operator, based both upon the distance between subscribers and on theduration of the call. In this connection it may be mentioned thatcharging on a duration basis may be efiected by repeat multifeemetering, but generally speaking it is usually considered preferable tolimit. the. multiple fee to a value of the order of four unit fees oreven less, as larger charges which cannot bechecked should preferablynot be made on a subscribers individual meter.

Another application of the invention isto the construction of a nationaltelephone exchange network which will permit calls being automaticallyset up by any subscriber toany other subscriber, regard being had to thedesirability of reducing interference to existing networks and trunk andtoll line layouts to a minimum, while at the same time keeping theadditional equipment to a minimum.

While the invention has particular application to known telephonesystems of the type'described above, it is not limited thereto, but itis adapted to be-used in addition in new-telephone-systems.

According to a subordinate feature of the in"- vention, calls set upfrom non-register-translator networks including main and satelliteexchanges toother exchanges or networks for which call recording isrequired, are routed under subscrib; ers control to a main or central"exchange or the calling network where route-determining means areprovided, for routing the call to the desired distant exchange ornetwork, automatic recording of the call being effected at the same mainor central exchange. I

While the characteristic feature of the invention as described aboverelates to the provision of route-determining and call recording meansat the same central exchange of a network there may be circumstances inwhich all calls from a non-register-translator network .fo'r'whi'ch callrecording service is required may pass through a nearby registertranslator network and according to a further feature of the invention asingle group of junction lines is provided between the central exchange(which may be a main exchange) of a non-register-translatbr network to acentral or sub-central exchange of a registertranslator network and "asan idle one of such.

junction lines would be automatically selected under subscriber controlthere is no necessity for providing any route-determining means at thecentral exchange of the non-register-translator network, and furtheraccording to this feature of the invention route-determining means wouldbe provided at the central or sub-central exchange of theregister-translator network while the call recording equipment would beprovided at the central exchange of the ncn-register-translator network,the distinguishing digits of the wanted exchange being transmitted undersubscriber control to the route-determining means at the central orsub-central exchange of the register-translator network.

According to a further feature of the invention in a telephonearrangement or like system comprising a register-translator networkhaving access to a plurality of other networks which may beregister-translator networks or non-registertranslator networks or both,the register-translator is adapted to be taken into use at theorigination of an inter-network call to route the call to a central orsub-central exchange of the register-translator network and a secondregistertranslator is adapted to be taken into use at said central orsub-central exchange to route the call to the desired network, callrecording equipment being also adapted to be taken into use at saidcentral or sub-central exchange for recording the 'call.

According to a further feature of the invention and particularlyapplicable in register-translator networks, a register-translator isprovided which is adapted either to route a call to an operatorsposition or to route a call to a call recording position forinter-network calls according to the value of the digit received afterthe registertranslator has been taken into use.

By this feature of the invention it is possible to utilise the existingarrangement whereby for calls to an operator the subscriber dials thedigit 0, in this case a call would be routed to an opera'to'r either bydialling digit 00 or by dialling the digit 0 and delaying to dial anysubsequent digit, while if a subsequent digit has followed the firstdigit other-than digit "0 then the call would be route'd'to'acallrecording position.

According to a further feature of the invention a regi-s'ter-translatornetwork may be extended by adding exchanges or exchange networks whichwould involve the possibility of calls being made between subscribers inthe extended network which should be charged for by call'rec'ording andaccording to a further feature of the invention a register-translator isadapted to be taken into use at the exchange at which or at a satelliteof which thecall originated while a second registertranslator is adaptedto be taken into use at a central or sub-central exchange by whichaccess is had to the wanted exchange, recording equipment being alsoadapted to be taken into use at a central or sub-central exchange toenable the call to be recorded.

A further feature of the invention .is concerned with specialarrangements to enable calls to be setup for a very large area ornationally according to which feature the network. covering the wholearea is dividedlinto a number of zones-each having one or morezonecentral exchanges and eac'hzone being. divided into. groups while thegroups ,in .turn each have one or moregroup-centralexchanges andeachgroup is sub-divided into a'number of exchanges or exchangenetworks.

aseascs each of;suchxexchanges or networks havlng'its ownlinkednumbering scheme. In such a net-i workaccording ,tothis feature of theinvention r nte-dete rmining means by which the routetro 'ng digits bywhich a call is to be set up from the calling groupor zone to the calledgroup or zone are determined, together with means for.

recording particulars of the call are located at a group centralexchangeor a zone central exchange in thecalling group or zone.

I The following arrangements correspond to subsidiary'featuresof theinvention which while they fare .protected in co-pending applicationshave particularapplication in carrying out-the features of theinvention.

Incall recording number of the calling line and according to onesubsidiary. feature of the invention the identity'of thjcalling'line isascertained and. stored at' the calling exchange on the initiationof thecall over. the" junction line and subsequently. the stored identity.together with that, of the callingex-- changeis transmitted to therecordingexchange on the termination of theconnection, 1 According toanother subsidiary feature of the invention mechanical impulsegenerators are providedffor storing digits dialled by a subscriberi-t'isnecessary to identify the. In

interienetwork calls a simplified form of register-..

translater equipment, which will be known by the term routediscriminating equipment, isutilised,

and in which on-suchw calls feecharging which is access to a mainexchange manual board is had by dialling the digits 00.

Fig. 4 shows the layout of a register translator network with a numberof tandem or sub-central until the appropriate equipment is in aposition to receive the same.

' Accordingto a further subsidiary feature of the invention theinformation to be recorded is stored until the end of the connection andis then transferred'to a recording or printer controlling unitatwhi'chother information is added and the whole of the information tobe recorded or printed is duly transferred in rapid manner to theprinter and recorder so that only a few printers and recorders need beprovided for a large number of recording positions. I

lAnother feature'of the invention which is particularlyfadvantageous foruse in transferring a number rapidly over the connection 'in code andexchanges'tl'ierein at which will be located call recording equipmentrequired in connection with certain types of calls either completedwithin the area or to exchanges or networks outside the area.

Fig. 5 shows a trunking-diagram for the routing and. recording of atypical call from an exchange within a register translator area to anoutlying exchange or networkvia a sub-central exchange. Fig. 6 shows thetrunking arrangements involved in local andsub-centralregister-translator exchanges when different classes oftraffic requiring calling subscriber identification are combined in acommongroup at a central exchange or point. Fig. Yfis concerned withtrunking arrangementsior the purpose of automatically setting up andrecording calls on a national basis and shows typical trunkingarrangements involved in ad'istribution of incoming calls at a zonecentre storing it in a cheap manner until it is required,

concerns'animpulse regenerator which is adapted to'respond to two setsofv pulses, the pulses of one iSBt having a definite timed relationshipwith respect to the pulses of the other set andin which the two sets ofpulses are adapted to be re-transmitted in substantially the same formas received." Conveniently the impulse regeneratoris constructed asdescribed in McClew and y -Wo0dlands UnitedStates Patent No. 2,188,461,

issued January 30, 1941, and according to the invention a member ismovedby a receiving magnet to an extent determined by one set of pulseswhile pins are displaced during such movement in responseto' a'secondset of pulses acting upon a marking magnet, such second set of pulseshaving a definite timed relationship with respect to the first set, animpulse' generator controlled thereby is adapted when released tooperate and generate pulses corresponding in number to said first set ofpulses and to the extent of movement of said member while a furtherimpulse generator is provided adapted to be operated as each displacedpin isencountered to generate pulses corresponding to the second set ofpulses.

These and other features of the invention will be better understood froma description of the following embodiments thereof which are given byway of example, reference being had tothe accompanying drawings.

Fig. l'shows the layout outof a number of such networks in which for.

V of two non-register translator telephone networks which may be twoexchange and also at a group exchange in the and 12 when arranged sideby side show the circuits of a toll line relay set. These pieces ofapparatus'f are particularly. adapted for use in register translatorareas of the type shown in Figs. 4 and 5, but it willv be appreciatedthat the circuits of equivalent apparatus in other areas may be designedon a similar basis.

For the purpose of identifying a calling point, identification andstorage equipment of the type disclosed in our Patent No. 525,902,issued November 28, 1940, may be utilised, while equipment and circuitson the general lines described in Ostlines application No. 278,729,filed June 12, 1939, may also be brought into use for the pur pose ofcarrying out the invention. 7

Reference should now be had to Fig. 1 andit will be understood thatintercommunication between the two networks shown and also betweeneither ofv these networks and other networks which are notshown wouldhitherto be effected via the manual boards of the main exchanges B and Cthrough which internetwork calls are set up, and arrangementswill bedescribed whereby such'calls may be set up and recorded automatically. i

i For the purpose of simplicity each networkis merely, assumed tocomprise a main exchange such as B or C and a number of satelliteexchanges suchas A and D and the setting up of calls by'subscribers onexchanges A'and B will now be considered, reference being had to thetrunking diagram of Fig. 2.

It will be understood that each network will have its own linkednumbering scheme, and a two or three digit code will be prefixed to thewanted subscriber's number in the case of inter-network calls. For thepurpose of discrimination between local linked number and inter-networkcalls, all calls of the latter class will be prefixedby a cornmonpreviously unused first digit, such as 8, followed by one or more prefixdigits together with the called number in the required network. Thedialling of a first digit 8 by subscribers having unrestricted accessfacilities will cause the connection to be routed at the main exchangeto a toll line relay set which can take into use translating and callrecording equipment, the translating or so-called route discriminatingequipment bringing about routing 'of the call to the required networkeither directly or via intermediate networks.

Considering the case of a call originated by a subscriber on thesatellite exchange A, it will be seen that two groups of junctions areassumed to be provided from this exchange to its parent exchange B,these being divided up into ordinary and high grade junctions.

When the subscriber removes his receiver he is connected via the linefinder LE to a discriminating selector repeater DSR associatedtherewith, and this switch thereupon-associates itself with an incomingselector ISR at the main exchange via the hunting switch U/S and theordinary junction line 10 in Well-known manner.

If the first digit dialled is any of the numbers 1-7 and 9 whichindicate that a subscriber in the local linked numbering scheme isrequired either'of satellite exchange A, of the main exchange B or ofany of the other exchanges in the calling network, selector repeater DSRafter having been stepped in parallel with the incoming selector ISR inaccordance with the digit dialled will either release the junction inthe case of a local or adjacent exchange call and connect up with alocal second selector, or will retain the junction connection and willrepeat subsequent digits dialled over the junction l0, incoming selectorISR and outlets such as [2 to switches connecting with the requiredsubscriber either on the main exchange B or on other exchanges in thecalling network directly connected to this exchange.

In case the first digit dialled is "0 the ordinary junction ill isreleased and the call is routed over the high grade junction II to themain exchange manual board, a suitable discriminating signal being sentfrom the satelllte'exchange out going relay set ORS to the main exchangediscriminating relay set DRS so as to cause the connection to be routedto the main exchange manual board jack 0. In case a coin box subscribershould be calling, a difierent signal will be extended to the relay setDRS so as to cause the connection to be routed to a coin box jack CB atthe main exchange manual board.

If the calling party wishes to set up an internetwork call, the firstdigit. dialled will be 8 in which case the ordinary junction I0 isreleased as before and the high grade junction I I is taken into usefrom the DSR level 8, a distinctive signal being transmitted from theoutgoing relay set ORS to switch the connection at the rel'ayset DRS tothe toll line relay set TLBS. Coin box subscribers dialling this digitandnot being enill titled to originate such calls on an automatic basisare barred access thereto either by the extension -of a suitable signalfrom the relay set ORS which causes the relay set DRS to transfer theconnection to the coin box (CB) jacks on the main exchange manual boardor due to the factv that there will be no access to the relay set ORSfrom level 8 of the special group of DSR switches provided forsuchsubscribers.

When the relay set TLRS isseized, access is had to an outgoing selectorOGS, while the hunter switch HS is caused to associate itself with anidle route discriminator RD. Before the question of call recording isconsidered, the routing of the call to its required destination will bedescribed, and in this connection one or more digits subsequent to thefirst dialled digit are received on the route discriminator effects thenecessary translation and transmits the required routing digits out viathe toll line relay set, the outgoing switch and subsequent switches togain access to the incoming switch at the main exchange of the desirednetwork. Ihe toll line relay set will be provided with an impulsestorage and regenerating device for instance of the electro-mechanicaltype disclosed in McClew and Woodlands United States Patent No.2,188,461, and this will serve to store the remainder of the digitsdialled during the transmission of the translated digits from the routediscriminator.

When the routing digits have all been sent out, the impulse storage andregenerating device in the relay set TLRS is caused to send out thedigits stored therein in untranslated form, so as to complete theconnection to the wanted party.

Considering the question of recording such calls, the minimum amount ofinformation required to enable the'call to be charged against thecalling subscriber will consist of the calling number and the callednumber, and if the call is to be charged on a time basis, the durationof the call, together possibly with the time and date.

For the purpose of calling number identification it will be understoodthat as a result of the setting up of an inter-network call, theoutgoing relay set ORS at exchange A will be caused, either during thesetting. up of the connection, or on reply of the called party, orduring or at the end of conversation, according to which proves the mostconvenient, to associate itself over finder switch RSF' with a storagecontrol relay set SC which in turn connects with an identificationcontrol relay set IC. This on being seized sets into operation anidentification switch SS which operates in the manner described inBritish Patent 525,902, whereupon the identity of the calling line willbe determined and stored in the outgoing relay set ORS, storing beingeffected as described for instance in British Patent 525,902.

In connection with the storing of the calling number at the originatingexchange until it is required at the exchange where call recordingequipment is provided, if this is effected by means of storage relaysand a uni-directional sending switch as described'in British Patent525,902, then it will not be necessary to provide the relay set SC andthe finder switch RSF since the calling number can be communicateddirect to the relay set ORS. Use might however be made of anelectromechanical storage andv regenerating device in the relay set CR8,and in this instance it may prove preferable to utilize a common storagecon trol set SC and finder switch R'SF as shown in which in responsethereto Fig. 2 in order that the signals characterising the identityofthe calling party may be firstly re- I ceived on either relays or astepping switch in the common relay set SC. The relays'or steppingswitch convert the signals received into markings suitable for settingthe 'regenerator in the-relayv 7 set-ORS in such a manner that thenumber can be subsequently retransmitted therefrom in code to thedistant exchange.

As regards the called number, the digits dialled into the toll linerelay set 'ILRS are stored for instance on relays and at termination ofconversation the hunter switch HS, which it will be notedhas its banksplit so as to gain access successively to' the route discriminator andto call recording equipment as required, is caused to associate itselfwith a printing or recording controller PCRS whereupon .the callingpartys numberwillbe transmitted thereto from the outgoing relay s'et'atexchange A and the junction'll will be released after-which the calledpartys number recorder controlling apparatus the tariiT being determinedat the end of conversation. I The general arrangement of the printer. orrecorder controlling apparatus may conveniently followvthe .designof theprinter controller as de scribed in Ostlines application No. 278,729filed June 12., 1939, suitably modified to meet the con-v ditionsdescribed above while the printer or recorder'itself will be such as tobe only taken into use when the information is ready for immediateprinting and recording.

Theroute discriminator described diners from the normalregister-translators such as are used in multi-exchange areasin that itis only required to receive initial digitsof a dialled number and'insatellite exchanges could of course be replaced by ordinary firstselector switches which on seizure would gain access to commondiscrimination equipment over a hunter switch, this discriminationequipment serving to determine whether the call was to be metered orto'be charged for by means of automatic call recording equipment andcausing the-connection to be routed at the main exchange accordingly.The discrimination equipment may generally follow the lines of thatdisclosed in Taylor and Bakers Patent No. 2,232,189, issued February 18,1941.

The invention is not limited to the simple example shown, as obviouslyeach network havin its own linked numbering scheme could have associatedtherewitha number of dependent networks, each having its own numberingscheme. If it wasconsidered desirable to ticket calls from an exchangein a linked numbering scheme to a dependent network thereon this couldbe readily effected in the manner already described and such calls wouldthen have a common prefix digit such as 8.

As a further extension of the scheme, a number of multi-fee areas eachcomprisin a plurality of exchange networks operating ona multipl feebasis for inter-network calls couldbe linked up automatically on a callrecording basis. In such a case recorded inter-area calls will be routedvia the centralexchange of each areaat which the call recordingequipment will be located and it may be that in some circumstances callsbetween exchanges in adjacent areas but which are only a unit feedistance apart will be completed on a, call recording basis. Coin boxsubscribers setting up such unit fee. connections would however berouted to a manual board.

In case no spare first digit is available for use on inter-network callsit might be arranged that for main. exchange manual board calls thedigits 1 00 would be dialed,'while for calls requiring re responsethereto to route the call to the required exchange or network whereasthe register-translator is adapted to receive a full dialled number andinresponse thereto to route the call right throughto the required party.If therefore the route-discriminator is adapted toperform the fullfunctions of a register-translator then the impulse storageandregenerator device in the toll linerelay set can servefor the purposeof storing the called number until this information is required for tollrecording purposes, and it will not be necessary to provide storagerelays in the toll line relay. set for this purpose.

. As regardscalls originated by main exchange subscribers, suchsubscribers gain access to the first numerical selector SR. over a leadsuch as l3 and the setting. up of calls which require recordingfollows-along the lines already described.

- Although in the arrangement described manual boardand inter-networkcallsare routed over one group of junctions, and ordinary linkednumbercalls over another group'of'junctions, a single group of junctions tothe main exchange may be provided to serve all classes of traffic,discriminating signals being utilisedto. efiect the correct routingof-the call at the main exchange.

.The discriminating, selector switches at the dialled.

cording digits 01-09 would be dialled.

Fig. 3 shows typical trunking arrangements at a satellite exchange A andmain exchange B in which levelO is utilised to gain access to dialledtoll exchanges. It will be seen that the equipment at exchange A followson the lines of that already described in connection with Fig. 2, adiscriminating selector repeater being provided in this exchange andhaving access to a high grade junction l l via an outgoing relay setORS.

If the first digit dialled is 0, access will behad to a discriminatingrelay set DRS at exchange B and in the case of an ordinar subscribercalling, if he fails to dial a further digit within'a predeterminedperiod the connection will be routed to the main exchange manual board.If

a coin box subscriber having restricted access is calling, theconnection will be immediately routed to the main exchange manual board.When the relay set DRS is seized it associates itself with a free tollline relay set TLRS over a hunter switch and this relay set receives thesecond digit If this digit is 0 thereby indicating that a-manual boardcall is required, a signal will be i sent back from the relay set TLRSto the relay set DRS so as to transfer the connection to the manualboard, but if the second digit is 1-9 then the toll line relay set willdirect this digit to a route discriminator. in the manner alreadydescribed in connection with Fig. 2. Call recording is subsequentlyperformed in the manner already described.

In the case of calls originated by main exchange subscribers, if 0 isdialled as a first digit access will be had from the selector S to astor--' age and discriminating relay set SDRS which functions in thesame way as the relay set DRS except that in addition it has provisionfor storing the identity of the calling party until this is required forcall recording purposes.

Outgoing toll calls from the manual board are handled via the jack O/Gwhich has access to the required by the route discriminator, the storageand regenerative device might be arranged only to re-transmitimmediately. those dialled digits which are required by the routediscriminator. The remainder of the digits dialled will then be helduntil all the routing digits have been sent out from the routediscriminator after which they may be retransmitted to complete thesetting up of the connection. 1

In case the DSR at the satellite exchange is replaced by an ordinaryselector switch having access to a common discriminating unit as pre-Viously mentioned, the storage and regenerative device in this unitcould be arranged to have a controlled sending-out facility therebyavoiding the use of an intermediate storage and regenerative device.

Areas to which the invention may be applied may include networks havingdependent networks and/or exchanges thereon and it is often usual in thecase of calls from dependent exchanges to dial one or more prefix digitsin order to gain access to the parent exchange. In such a case if a callrequiring call recording facilities is required, the number of digits tobe dialled would include the initial prefix digits to gain access tothemain exchange, the digit or digits required to Y route the connectionvia the intermediary of the route discriminator, together with thecalled number on the wanted network. In order therefore that the numberof digits to be dialled might be reduced, equipment might be provided atthe various dependent exchanges which, in response to the dialling of adigit or digits indicating a call requiring call recording facilities,would elTect a predetermined translation to route the call to commonroute discriminating and/or call recording apparatus at the mainexchange, after which some or all of the initial digits would betransmitted thereto together with the remainder of the digits dialled inuntranslated form.

The arrangement described with relation to Fig. 3 assumes that the trunkline relay set TLR-S has access both to route-determining arrangementsas well as to call-recording apparatus in the same way as in Fig. 2, butin the case of calls to or through a register-translator network whichmay in fact be the only calls for which call recording facilities are tobe provided, a single group of directjunctions is provided from a mainexchange, such as B, to a central or the subcentral exchange mostconveniently situated forreceiving calls from thenon-register-translator network. In such as case there is no necessityfor providing special route determiningmeans, at the central exchange ofthe non-register-translater network, the route being already deter- 'ofthe wanted party may be translated.

Considering new methods by which the scope of multi-ofiice areas of theregister-translator type can be extended so as to include outlyingnetworks or exchanges, and by which calls therebetween can be chargedeither on a call record ing or a multi-fee metering basis in accordancewith the particular conditions obtaining there are two preferablemethods which can be utilised in the case of extension to existingnetworks.

According to one method the unusable codes in a register-translator areanumbering scheme are used for the purpose of handling calls to outlyingdistricts thereof. It is appreciated that most of these codes cannot bearranged to represent thefirst letters of an exchange name but they caninstead be used either as numerical prefixes or alternatively on a mixedletter and numerical basis if this should prove to be preferable fromthe subscribers point of view.

In another method advantage is taken of the fact that at present thedialling of digit 0 in a register-translator area causes the seizure ofa register-translator adapted to be seized also when some other digit ordigits are dialled, different kinds of access being provided so thatsaid register translator will route the call either to an operatorsosition in response to the dialling of digit 0 or to another subscriberin response to other digits. It is proposed that a special set of 0level simplified register-translators shall be provided, it beingarranged that all calls requiring the use of call recording equipmentare preceded by the digit "0 followed by other extra digits as required,and the full number of the called party in the wanted exchange.

If the first digit dialled is "0 and is not followed by another digitwithin a short interval of time, say three seconds, the call will berouted to a manual board via which a long distance call may be completedif desired, while the call will also be routed to this manual board ifthe digits "00 are dialed, the dialling of these two digits being thenew method of calling an operator.

If digits 01 to 09 are dialled as the first two digits access to routesrequiring call recording facilities will be provided. If the 0 only isdialled as a first digit by a coin box subscriber he is eitherimmediately routed to a manual bord or given NU tone from one of thefirst code selectors which would be takeninto use by such subscribers.

Each exchange will thus be provided with a single group of 0 levelregister-translators which give access to means forrouting long distancetraffic whether this is handled either on a full automatic basis or viaa manual board. These register-translators are in turn arranged to giveaccess to call recording and/ or register-translator apparatus groupedat a central exchange in the area.

A description will first be given of the first scheme by reference tothe register-translator layout of Fig. 4. Four of the exchanges shownshaded A-D within the existing area as defined by the dotted line areassumed to serve as subexchange 'F and in which the is on :exchangeE, itwill be assumed by way of central exchanges. Callsto outlying networksor exchanges suchas E will be routed via one or more sub-centralexchanges,-at which call recording equipment will be provided inaddition to registertranslator equipment.

It will be understood that certain of the exchanges within the normalregister translator- "area but near the fringe thereof may be operatedcation being initiated and stored at the calling exchange at anyconvenient stage during the call.

It may be that calls to the outlying exchange E can be set up on asingle or multi-metering basis owing to the close'proximity of thecalling and called exchanges, and in such a case calls to exchange Ewill be operated on an ordinary single on 'a single or multi-mete'ringbasis to exchanges outside'the area, while calls from other exchangeswithin the area to the same outlying exchange will be operated on thecall recording basis. Againit call recording for cerfor instance whensuch maybe. desirable to utilise tain calls within the area,

"calls extend from one end of the-area to the other.

' Considering now the case of a call originated at example that therequired subscribers number is 746.9762, the "digits 746 being asuitable previously unused code in the register-translator area.

Reference should .now'be had to the trunking diagram of Fig.95. Acalling party on removing his receiver will be connected via hisuni-selector U/Sto a first code selector ICS at the local exchange whichthereupon in known manner associates itself with an idle A digit switchLADS over the hunter switch LADI-I. In response to the dialling of thefirst digit 'lone of the level 7 group of local register-translators LRTwill be taken in useand will receive the remainder of the digitsdialled. The second and third digits dialled;

required subscriber or multi-meteling basis when originated bysubscribers at exchange B and possibly in the near vicinity thereof,while calls to exchange E from other exchanges in theregister-translator area will be operated on a call recording basis.Under these conditions the same group of register translators at the allclasses of call since the existing register-translators will alreadyhavebeen arranged to cater for routing out to the outying exchange involved.

. In the case of calls from say exchange H to exchange E,it is feasiblethat the six translations normally available in the existingregister-translater at exchange H will be suflicient to allow .for theprovision of routing out to the required exchange Eand also forrepeating the dialled three. digit code to the tandem exchange B. Inthis case therefore there will be no necessity to take into use aregister-translator at the tandem exchange, and the toll line relay setthereat if call recording "is require-d will simply store the called.number until the end of the conversation.

namely 46, are thereupon translated to, say985.

soas to route the call via exchanges such as-D and G to the sub-centralor tandem exchange .13

having access to the outlying exchange E. The

routin digits are then followed by the complete number dialled, namely746.9762, which will be required at said exchange B both for the purposeof enabling the call to be routed out to the desired network orexchange, and also for the purpose of call recording. The transmissionof the routing digits 985 will gain access via the sub-central incomingselector 'IISR to a switch THS, the banks of which are split so as togain access successively to A digit switches andcall recording equipmentasrequired'.

During the hunting or the switch TI-IS a signal will be sent back tohold uptheregister-trans lator at the local exchange and when anidleswitch TADS has beenfound, the local registertranslator LRT willcommence to send outfthe complete number dialled. v, p

The register-translators such as TRT taken into use at the tandemexchange may be in a special group arranged to provide translations forrouting calls to outlying exchanges and/or net- 2 works served by thetandem exchange, which net works may include one or more registentranslator networks. As before, digit 7 will be received on the A digitswitch and subsequent ldigits will be on the level 7 group ofregister-translators toll line relay set such as TLRS, and thisthereupon associates itself with an idle A digit switch TADS over thehunter gain access with the called party It isuappreciated that whereexisting register it will not be possible translators .are made use ofto cater for more than four numerical digits in addition to the codeletters and/or digits, and

in some circumstances it may prove desirable to modify the existingequipment so as to provide for the storing of five or more numericaldigits;

Consideration will now be given to the second proposed method by J whicha special group of register-translators is provided in an originatingexchange for handling. calls requiring call recordingfacilities whetherrecording be effected manually by an operator or automatically.

,Sincethe number of routings to be made by these translators will besmall compared with the numberof'translations'to be made by translatorsserving other A.- digit switch levels, they may be of simplerconstruction. As described in connection with the first method it isnecessary when setting up a'recorded connection to route the callthrough'from the calling exchange to a sub-centralexchange which handlestraffic to the call' recording required exchange after which thecomplete number dialled is repeated thereto and for the purpose ofstoring and re-transmitting the wanted numberthe special group of 0*level register translators maybe provided with electromechanical"impulse storage and regenerative mechanisms, of the type alreadymentioned.

- As a preferred alternative it may be arrang d that when for instance acall is originated at exchange F in Fig. 4 and is destined for exchange1 E, the "0 level register-translator at xchange F will not, asdescribedalready, route the call directly to-the tandem exchange Bnearest to the outlying exchange E. in response tothe dialling of a tollcode'numbercommencing with digits 01-09, but will; simply route the callto the parent tandem exchange D of the calling'exchange F and at thisexchange D there will be located the equipment for exchanges such as eThe advantage of this scheme is that the 0 level translators at eachgroup of exchanges op eratinginto a parent tandem'exchange will onlyhaveito have provision-for effecting two routings,

tandem exchange B will be used for one to a manual board .at the parenttandem exchange and another to a relay set thereat which has accessfirstly to a register-translator or route-discriminator which efiectsrouting of the call to the required outlying exchange and secondly tocall recording equipment. This method enables the equipment in the levelregister-translators to be reducedto a minimum;

Such an 0 level register-translator is described later with reference toFigs. 8 and 9.

In connection wtih the handling of call recorded trafiic it is furtherproposed according to the invention that all types of traflic requiringidentification of the calling party should be combined in a common groupto a central point, and in order that certain types of subscribers, forinstance coin box subscribers, may have restricted access facilities,access will be had to this common group from two different switch levelsone Of which is barred on those selectors serving the specialsubscribers having restricted access. Means will be provided at saidcentral point to separate the various types of trafiic.

Referring now to Fig. 6 it will be seen that two groups of first codeselectors ICS (CB) and 108 are provided at the calling exchange for coinbox and regular subscribers respectively, each having access to the samegroup of local register translators LRT, the other equipment involvedbeing the same as that described in connection with Fig. 5. Both theregular and coin box first code selectors have access over level such as8 to the outgoing junctions to the main xchange, and this level would beused in the case where either type of subscriber required access to amanual board at the subcentral exchange. In accordance with theparticular routing digit received on the incoming selector 'I'ISR at thesub central exchange, access will be had either to an ordinary manualposition via the jack designated 00 or to trunk, toll'or telegram.positions via the jacks labelled TRU, TOL and TEL. Other types ofconnections which require to be set up via a manual position may begiven access via other levels of selector TISR to different jacks.Suitable discrimination will be given to these positions as to whichtype of subscriber is calling whether ordinary or coin box, thediscriminatory signals being transmitted from the outgoing relay set ORSin accordance with the particular type of first code selector from whichit has been seized. In the case of. a call originated by an ordinarysubscriber, it could either be arranged that immediately the operatorplugged in to the jack subscriber identification equipment will bestarted up from the outgoing relay set ORS at the local exchange, afterwhich the calling number will be transmitted to the central point oralternatively the actual starting. up of the identification equipmentcould be under control of the operator. This latter arrangement would begenerally employed from the 00 operators position since such an operatormay in some cases be merely assisting subscribers, while in other casesshe may complete a call therefor possibly to some exchange whichrequires'call recording facilities when she will require to know theidentity of the calling party. In all these cases the calling numberwill be preferably displayed on some form of indicator in front of theoperator, the actual period of display being under her control.

It will be noted that level I of the incoming selector TISR is arrangedto connect via a toll relay set 'ILRS to outgoing selectors SRI anddiscriminators will also SR2 and it will be arranged that where acalling party desires such a connection, the first code selector at thelocal exchange will be raised to a level such as '7, so that if thecalling party is a regular subscriber the connection can be completed inthe manner described in connection with Fig. 5, While if the callingparty is a coin box subscriber, the connection will not be completedbecause the coin-box first code selector 103 (GB) does not have accessto the outgoing junctions over level 7. A "number unobtainable tone insuch a case will be given to the calling party and theregister-translator taken into use will be released.

In regard to incoming calls from outlying ex ohanges to a. multi-ofilceregister-translator network, direct junctions will be provided from thecalling exchange or the main exchange of the calling network to one ofthe central or subcentral exchanges in the register-translator net Work.The incoming junctions will preferably be terminated on a new rank offirst code selectors and these will have access to the ordinaryregister-translators provided in the sub-central exchange, and therouting of calls to exchanges within the register translator area willproceed in the ordinary well-known manner. As regards the charging ofsuch calls, discriminating equipment will be provided at the originatingexchange to determine whether charging shall be on an ordinary meteringor call recording basis. These be provided with impulse storage andregenerative devices so as to enable some or all of the digits dialledtherein to be repeated to the sub-central exchange for the purpose ofsetting up the call via the sub-central register-translators. In case acall requires recording, the discriminator at the originating exchangewill be arranged to'transmit a signal to the sub-central exchange so asto cause call recording equipment to be taken into use. The recordingequipment will store particulars of the wanted partys number duringconversation, while the identity of the calling party will be determinedand stored at an outgoing relay set in the originating exchange. At theend of conversation a printing or recording controller will be takeninto use and the particulars required for charging purposes will becommunicated thereto in the manner already described.

In the typical trunkin diagrams of Figs. 1-6 which have now beendescribed, the circuits of most of the items ofapparatus involvedtherein are known to those versed in the automatic telephone switchingart, while in some cases relevant patent specifications have been cited.

Consideration will, however, :be given to the circuit operationsinvolved in setting up calls via the intermediary of a simplified 0level register-translator located at an exchange such as F in theregister-translator area of Fig. 4, it being assumed that suchregister-translators are adapted in response to the dialling of digit 0,or digits 00 to route the call to a manual board at the parent tandemexchange D, and in response to the dialling ofjany of the pairs ofdigits 01-09 to route the call to exchange D, after which the completenumber dialled, with the exception of the first digit 0 which is of nofurther use in the setting up of the call, is repeated in unchanged formthereto.

Atoll line relay set is taken into use at exchange D and gains accessfirstly either to a register-translator which has facilities for routingthe call to any of the outlying exchanges is earthedat the first codeeither directly or via-the intermediary of other exchanges in the area.

tandem exchange manual board ortoll line relay set in accordance withthe particular second digit dialled.

For the purpose of routing and call recording it is also necessary tohave details of the full called number at the tandemexchange and thestorage and retransmissionof this information is effected by meansof amechanical impulse and storing-regenerative device of the type alreadymentioned.

Considering the circuit operations, it will be understood-that thecircuits of the first code selector and A digit selector 'may be of thetype disclosed in our British Patent No. 469,184 which also disclosed atypical ordinary register-translate-r. When an A'digit selector switchseizes the 5 level register-translator of Figs. 8 and 9 in response tothe dialling of the first digit 0,, its

wiper switching relay responds to battery mark-,

ving the idle condition of the register translator.

Such battery is connected to the P lead via the upper'winding of relay Ain paralle1 with resistance YA andthereupon extends an earth forwardto-operaterelay A, whereupon relay B is operated in series withthemagnet RM (non-operative in this condition), and this relay in turnbrings up relay BBQ Relay BB in operating at armature bb3 brings uprelay P, at armature bb5 extendsealth on to the common motor start leadH to set in operation the S and Z pulse delay timing equipmentassociated with relay TP and M and to set in operation the motor whichdrives the impulsing springs IMPI and IMPZ required by theregister-translator for sending out the translated dialled code. Atarmature'bbl an impulsing circuit'is prepared to a regenerator receivingmagl net RM, at armature bb8 an impulsing circuit is prepared to themagnet FM of the reverse drive electro-magnetically operated switch F,while at armature 'bb9 the upper winding of relay A is disconnected fromthe incoming P lead but this relay remains held over the pulsing lead PUwhich selector impulsing relay armature. I

The dialled digitreceived at the register-translater will beany'of thedigits 1-0 and this will be received on relay A Which' in respondingthereto at armature a2 repeats the impulse train to the magnet FMand-steps the switch wipers roundto a position corresponding to thedigit dialled. At the'same time at armature al the impulse trainisrepeated to the regenerator receiving magnet RM, it being noted thatresistance YB in series therewith is now short-circuited by armature bblso as to enable the magnet to respond to the impulses; the resistance YBserves to prevent premature operation of'the magnet RM during theenergisation of relay A. During the impulse train relay B isintermittently short-circuited by armature al but it remains operateddue to the slugging effect of the short-circuiting, while relay Coperates on the first release of relay A and subsequently holdsthorughout the train, and at its armature cl energisesjthe regeneratormarking magnet MM.

Considering briefly the'lmpulse storing and rereceives the second digitThe toll line relay set also can gain access to call recording equipmentI comprises essentially a generating device, it will be understood fromdetails given in the prior specification that it receiving disc and,sending disc which are arranged on either side of a plate carrying acircular row of pins. The receiving disc is rotated step-by-step inresponse to the impulses received on the magnet RM and carries with it amarking lever which is released on deenergisation of the marking magnetMM at the end of. each train of impulses, and pushes a pin correspondingto the digit dialled through the pin plate into the path of the sendingdisc. For each digit received a corresponding pin is pushed through theplate and these pins serve to regulate the movement of the sending discwhich controls .the generation of outgoing impulses by the re.-generator impulse springs IMP3.

1 Returning again to the storage of the first digit on the regenerator,when the magnet RM responds and commences to rotate the receiving discstep-by-step, the first movement of this disc brings about themechanical operation of the regenerator off normal springs and a circuitis thereupon prepared for relay ON over contacts NI At the end of theimpulse train relay A remains steadily operated and on release of relayC after its slow period governed by the short-circuiting of its winding,the circuit for themarking magnet MM is opened andthis magnet restoresthereby causing the lever carried by the receiving disc to release andto push a pin corresponding to the digit dialled into the path of thesending disc. I

Atthe same time the contacts mm controlled by the marking magnet closeafter having been opened during the energisation of the magnet and in sodoing complete a circuit for relay ON which thereupon operates and locksfor the remainder of the setting operation over its armature on! andoid-normal contacts NI to earth.

While the magnet RMofthe regenerator is being operated over contact al,th'e'magnet FM of switch F is'operated over contact a2 so that thesecond digit is registered on both the regenerator and the switch F.

It will be remembered that in case the calling subscriber wishes to gainaccess to a manual board subscriber, the two digits 00 will be dialledin which case the second digit 0. will be stored on the regenerator,while the switch F will be set to position ll. Contact II on the F4 bankis cross connected to a terminal 12 so that on release of relay C at theend of the train earth is extended over wiper and'bank F4 to bring uprelay SM, which in amanner to be later described initiates the routingof the call to the manual board. Contacts 2-l 0 on the F4 bankcorresponding to a second digit 19 which are dialled when a toll call isbeing set up, are cross connected to a terminal I3 so that relay SC isoperated in this case and at armature s02 completes a locking circuitfor itself.

In response to the dialling of digits 1-9 as a second digit, theregister translator is caused to send out'trains of pulses to effect therouting of the call to the parent tandem exchange and hence when relaySC operates a circuit is prepared to relay IG. 7

Connected in parallel with this relay are a pair of impulsing springsIMP2, which it will be understood are operated in conjunction with theoutgoing'lo'op impulsing springs IMPI in such a manner that when springsIMPI are closed the IMP2 springs are open and vice versa.

The motor controlling-these impulse springs has previously been set intooperation, and when impulsing springs IMPZ make their first break aftertheoperation ofrelay SC,.relay IG. isoperated. At armature igl. theimpulsing. springs IMPE are connected up. tov the. magnet PM of switch Fand at armature igZ a short-circuit-is removed from theimpulsing springsIMPI At armatures 2'93 andz'g4 the circuits to relaysSC and SM aredisconnected fromthebank. F4. of switch F, and bank FB-is now connectedupv at armature ig5 to relay SZ so that it may now be used for thepurpose of controlling the total numberof trains of impulses to be sent.out from the register-translator. At armature igB theearth supply towipers F4 and F8 is rendered independent of the armature 02 so that iffurther impulse trains are being received during the ensuingtransmission, each resultant operation andrelease ofrelay C will bewithoutefiect: on this part of the circuit.

The above-described. relationship between: the impulse springs'IMPl andIMPZ. is suchthat for each step the F switch is causedto take by. meansof the impulse springs IMPZ an impulse willbe sent out over theleft-hand negative and positive conductors via the impulse springs IMPL.Initially, however, the impulse springs IMP! are shortecircuited over apath including resting armature $7714 and wiper F2 in. any of thepositions. 1-11. and strapping connection to. terminal I5 connected'withtheupper side of the-impulse springs.

It will be. assumed. at this stage. that for the purpose of routing thecall through to a toll line relay set. at the parent tandem exchange; itwill be necessary for the register-controllerto transmit the routingdigits 3148 and; these routing digits will be therefore transmittedin.response to the dialling of any of the pairsof. digitsOl-OQ indicativeof a tollcall.

Considering now the stepping ofthe switchF by the impulse springs IMP2,itwillbe seenthat impulse springs IMPI. areineffective until wiper F2reaches the 12th positionzwhen the short,- ci-rcuit is removedtherefrom. Three impulses will be delivered to line during thetransitof.wiper F2 to position 15 and these serve in known man nor to raise thefi-rstcode selector wipers stolevel 3. The next four contacts on. thebank are strapped so that as the wiper stepsv over these contacts, theimpulse springs again remainshortcircuited and bythis means aninterdigital pause is provided. Thesucceeding codedigits .1, .41 and 8are produced inlike manner the control of wiper FZbeing transferred to.wiper Ffiiwhen the wiper F2 leaves its bank and the call is routedto thetandem exchange via an .outging relay set.at the originating. xchangewhich will be shortly described.

When the F switch wipers Ffi reach position 40 all routing digits willhave been sent out and-a circuit is therefore. completed over wiperF8.-in position 40; to operate relaySZ which looks at-its armature eel,disconnects-the driving. circuit to the magnet FM .at armature s22 andat armature s23 short-circuits theimpulsing spring IMPI and introducesinto the outgoing loop. the. regenerator imp-ulsing springs IMP3.

At this stage of the call atoll line-relayset at the parent tandemexchange will have been seized and this relay set willbe endeavouring.to gain access. to one of axcommon group ofregistertranslators suitable.for routing. the; call to. the required outlying exchange. Inordertoprevent thegsendingi out. of; further. digits until. an idle routing.register translatorhas been: seized. it is arranged thatthebattery-connections to the line at the toll relay set are=normally suchthat relay D. will be inoperative.

When a free register-translator isfound, the battery connection.is-reversed so that rectifier MRA' becomes conductive and-rectifier MRBnonconductive and'relayD-now operates. Relay D in operating energises.relay. SS at armature d3, Wliereuponan energisingcircuit is completedfor the regenerator transmitting magnet TM.

It will now be understood that the pin in the regenerator' which wasdisplaced to mark. the termination of: the sending out. of the previouscall is pushed out of thepath. of the sending disc and back toits-normal positionby, a resetting pin, designated RP-and. in circuitwith relay P, but owing to the stepped head on the reset pin the sendingdisc'is not immediately released and: remains.held until magnet. TM is.de-energised. Magnet TM at its, contacts tm' disconnects relay P-whichthereupon opens the magnet energising circuit at armature p2 and asfully described in McClew and-.woodlands Patent N0..2,188,461 thesending'discv is. releasedand rotates until the reset pin comes upagainst the stop pin indicating the; termination; of. the first train.of impulses received thereon.

Duringthe sending out. ofthe train, it will be noted; that sincethezreset pin RP is not. connecting with any stop .pin such as-SP,relayP cannot be re-operated. while during this time the firstdigitreceivedv on the register-translator is sentout inregenerated. formby way of the impuls springs IMP-l controlled from the regeneratordevice and is delivered tothe routing reg:- ister-translatortaken inuseatthe tandem exchange.

On release of relay P it will be noted that a circuit is completedviaarmature 102 for the slowto-release relay ISwhich-serves for the purposeof timin the subsequent. interdigital pause.

Previous to. and during this time, further trains ofv dialed'impulsesmay be. received on the receiving. disc and-it will-be appreciated thatthe two operations of reception of certain digits andretransmissionofearlier digits may go on simultaneously-butindependently of each other.

When the, sending. disc comes. up; against the stop-pinindicating, thetermination of the first train of impulses, relay, P is againoperatedand relay IS is disconnected. After therelease time of. relay ISwhich determines the interdigital pause, the. sending magnet TM. againreceives a momentary energization inorder. torelease the sending discvonce more to generate asecond train ofimpulsesin the manner described.

When all thedigits. received have been retransmittedthe sending discwill catch up with the receiving disc; whereupon the off-normal contactsNI open and release-relay ON. Furthermore, if the. completenumber-.has-be'en dialed and sent'out. correctly theroute-discriminatorwill receive. a-full set of digits for routing the call to thewantedparty and asa result the .batteryconnections tothe lineconductorsare restored to normal so that relay Dreleases andextends-earth over armature dl; p3,- ss2 and 1292-, F. switch wiperF3-:or F! and bankarmature-onli to battery via relay C'O.

Relay COinope-rating at armature col :disconmeets the idlemarkingbattery'from theincoming P lead,- whereupon the wiperswitchingrelay in the Adigit-tselector istreleasech This-relayin releas-

